[thanos] Query functionality ramp up

[viennaa]

Context

The first draft of the Thanos plugin should enable a Thanos Query to talk to Thanos Sidecar as a store. For now it will fetch metrics from Prometheus deployed with kube-monitoring.

Acceptance criteria

• [x] Thanos Query deployed and reachable
  • [x] https://github.com/cloudoperators/greenhouse/pull/308
• [ ] kube-monitoring enhanced to spin up thanos-sidecar with objectstore config
• [ ] sidecar configured as store
• [ ] helm-chart
  • [ ] test added
  • [ ] merged #183